docs: add header

Author: jokasimr

docs/user-guide/estia/polcal.ipynb

@@ -99,10 +99,18 @@
     "i0, Pp, Pa, Ap, Aa, Rpp, Raa"
    ]
   },
+  {
+   "cell_type": "markdown",
+   "id": "4",
+   "metadata": {},
+   "source": [
+    "## Calibration and correction experiment"
+   ]
+  },
   {
    "cell_type": "code",
    "execution_count": null,
-   "id": "4",
+   "id": "5",
    "metadata": {},
    "outputs": [],
    "source": [
@@ -176,7 +184,7 @@
   {
    "cell_type": "code",
    "execution_count": null,
-   "id": "5",
+   "id": "6",
    "metadata": {},
    "outputs": [],
    "source": [
@@ -266,7 +274,7 @@
   {
    "cell_type": "code",
    "execution_count": null,
-   "id": "6",
+   "id": "7",
    "metadata": {},
    "outputs": [],
    "source": [
@@ -278,7 +286,7 @@
   },
   {
    "cell_type": "markdown",
-   "id": "7",
+   "id": "8",
    "metadata": {},
    "source": [
     "| Property       | On $Q$       | On $\\lambda z$       | Calibrate on $\\lambda z$, correct on $Q$      |\n",